This award represents the transfer of CAREER-grant funding for the research of Professor Stephon Alexander from Haverford University to Dartmouth College.
The search for a quantum theory of gravity has seen progress with the advent of string theory and loop quantum gravity, but both lack direct contact with experiment. The PI proposes a five-year plan that can potentially resolve fundamental problems in cosmology and particle physics by developing new models that arise from theories beyond the standard model and quantum gravity. Additionally, he proposes new observational schemes to test these models. The PI's long-term research plans over the next five years focus on two themes. One is at the interface of particle physics and cosmology where he hopes to look at the consequences for LHC physics of his new model that unifies gravity with the electroweak force. He will also investigate the phenomenological consequences of a Supersymmetric extension of this model. The second area concerns the nature of the cosmological singularity. The PI has proposed several novel theories based on modifying gravity and will also consider the experimental consequences of these models.
This project is also envisioned to have significant broader impacts. The outreach part of this CAREER project will consist of the PI giving a two-week course on Music and the Cosmos, which will be hands on presentation on the physics of sound and musical instruments. These lectures will be presented to urban high school students. The PI will also serve as both a research and long-term career mentor for two minority undergraduate students each year, by creating two summer research positions in his group through this award.
. In this spirit, I focussed on identifying model independent probes of perhaps the most compelling fundamental theory, string theory. Over the last three decades, string theory has evolved as a theory that unifies all four forces of nature. However, making contact with experiment has proven to be elusive. My CAREER proposal was based on original work by the PI and his collaborators. String theory is best formulated in 10 dimensions of spacetime. There are many ways to realize our four dimensional world in string theory. This multiplicity of realizing the real world is the source of experimental contact. The PI has shown that there are new interactions beyond the standard model that can show up, independently of the many ways that the four dimensional world appears in string theory. These interactions involve a left-right asymmetric configuration between gravitational waves and a spin-zero field (the universal string axion). As a result, if this string axion is non-vanishing in the universe (ie. if it contributes to dark energy, or dark matter) then left-right (parity violating) gravitational waves will propigate. The outcomes of my NSF CAREE proposal was to show that these parity violating gravity waves can be detected in binary astrophysical systems, such as binary black holes or binary pulsar systems. With my collaborators, the PI also showed that parity violating gravitional waves could be constrained in future cosmic microwave background radiaition, a relic from the expanding big-bang paradigm. The PI also proposed a new model that combines (unifies) Einstein's theory of general relativity and the electroweak interactions. In my CAREER proposal I set out to improve and study my model to identify observational signals for my theory for upcoming experiments at the Large Hadron Collider. I am pleased to say that I have published two papers that have identified new interactions that could be tested in upcoming particle physics collider experiments. These interaction involve a mixing between the higgs boson and the sterile neutrino. If the sterile neutrino is a good dark matter candidate then this may be a particle physics probe of the dark sector using Higgs phenomenology at colliders.
